/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/

This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it freely,
subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
///btSparseSdf implementation by Nathanael Presson

#ifndef _14F9D17F_EAE8_4aba_B41C_292DB2AA70F3_
#define _14F9D17F_EAE8_4aba_B41C_292DB2AA70F3_

#include "btCollisionObject.h"
#include "btGjkEpa2.h"

// Modified Paul Hsieh hash
template <const int DWORDLEN>
unsigned int HsiehHash(const void* pdata)
{
    const unsigned short*    data=(const unsigned short*)pdata;
    unsigned                hash=DWORDLEN<<2,tmp;
    for(int i=0;i<DWORDLEN;++i)
    {
        hash    +=    data[0];
        tmp        =    (data[1]<<11)^hash;
        hash    =    (hash<<16)^tmp;
        data    +=    2;
        hash    +=    hash>>11;
    }
    hash^=hash<<3;hash+=hash>>5;
    hash^=hash<<4;hash+=hash>>17;
    hash^=hash<<25;hash+=hash>>6;
    return(hash);
}

template <const int CELLSIZE>
struct    btSparseSdf
{
    //
    // Inner types
    //
    struct IntFrac
    {
        int                    b;
        int                    i;
        btScalar            f;
    };
    struct    Cell
    {
        btScalar            d[CELLSIZE+1][CELLSIZE+1][CELLSIZE+1];
        int                    c[3];
        int                    puid;
        unsigned            hash;
        btCollisionShape*    pclient;
        Cell*                next;
    };
    //
    // Fields
    //

    btAlignedObjectArray<Cell*>        cells;
    btScalar                        voxelsz;
    int                                puid;
    int                                ncells;
    int                                nprobes;
    int                                nqueries;

    //
    // Methods
    //

    //
    void                    Initialize(int hashsize=2383)
    {
        cells.resize(hashsize,0);
        Reset();
    }
    //
    void                    Reset()
    {
        for(int i=0,ni=cells.size();i<ni;++i)
        {
            Cell*    pc=cells[i];
            cells[i]=0;
            while(pc)
            {
                Cell*    pn=pc->next;
                delete pc;
                pc=pn;
            }
        }
        voxelsz        =0.25;
        puid        =0;
        ncells        =0;
        nprobes        =1;
        nqueries    =1;
    }
    //
    void                    GarbageCollect(int lifetime=256)
    {
        const int life=puid-lifetime;
        for(int i=0;i<cells.size();++i)
        {
            Cell*&    root=cells[i];
            Cell*    pp=0;
            Cell*    pc=root;
            while(pc)
            {
                Cell*    pn=pc->next;
                if(pc->puid<life)
                {
                    if(pp) pp->next=pn; else root=pn;
                    delete pc;pc=pp;--ncells;
                }
                pp=pc;pc=pn;
            }
        }
        //printf("GC[%d]: %d cells, PpQ: %f\r\n",puid,ncells,nprobes/(btScalar)nqueries);
        nqueries=1;
        nprobes=1;
        ++puid;    ///@todo: Reset puid's when int range limit is reached    */
        /* else setup a priority list...                        */
    }
    //
    int                        RemoveReferences(btCollisionShape* pcs)
    {
        int    refcount=0;
        for(int i=0;i<cells.size();++i)
        {
            Cell*&    root=cells[i];
            Cell*    pp=0;
            Cell*    pc=root;
            while(pc)
            {
                Cell*    pn=pc->next;
                if(pc->pclient==pcs)
                {
                    if(pp) pp->next=pn; else root=pn;
                    delete pc;pc=pp;++refcount;
                }
                pp=pc;pc=pn;
            }
        }
        return(refcount);
    }
    //
    btScalar                Evaluate(    const btVector3& x,
        btCollisionShape* shape,
        btVector3& normal,
        btScalar margin)
    {
        /* Lookup cell            */
        const btVector3    scx=x/voxelsz;
        const IntFrac    ix=Decompose(scx.x());
        const IntFrac    iy=Decompose(scx.y());
        const IntFrac    iz=Decompose(scx.z());
        const unsigned    h=Hash(ix.b,iy.b,iz.b,shape);
        Cell*&            root=cells[static_cast<int>(h%cells.size())];
        Cell*            c=root;
        ++nqueries;
        while(c)
        {
            ++nprobes;
            if(    (c->hash==h)    &&
                (c->c[0]==ix.b)    &&
                (c->c[1]==iy.b)    &&
                (c->c[2]==iz.b)    &&
                (c->pclient==shape))
            { break; }
            else
            { c=c->next; }
        }
        if(!c)
        {
            ++nprobes;
            ++ncells;
            c=new Cell();
            c->next=root;root=c;
            c->pclient=shape;
            c->hash=h;
            c->c[0]=ix.b;c->c[1]=iy.b;c->c[2]=iz.b;
            BuildCell(*c);
        }
        c->puid=puid;
        /* Extract infos        */
        const int        o[]={    ix.i,iy.i,iz.i};
        const btScalar    d[]={    c->d[o[0]+0][o[1]+0][o[2]+0],
            c->d[o[0]+1][o[1]+0][o[2]+0],
            c->d[o[0]+1][o[1]+1][o[2]+0],
            c->d[o[0]+0][o[1]+1][o[2]+0],
            c->d[o[0]+0][o[1]+0][o[2]+1],
            c->d[o[0]+1][o[1]+0][o[2]+1],
            c->d[o[0]+1][o[1]+1][o[2]+1],
            c->d[o[0]+0][o[1]+1][o[2]+1]};
        /* Normal    */
#if 1
        const btScalar    gx[]={    d[1]-d[0],d[2]-d[3],
            d[5]-d[4],d[6]-d[7]};
        const btScalar    gy[]={    d[3]-d[0],d[2]-d[1],
            d[7]-d[4],d[6]-d[5]};
        const btScalar    gz[]={    d[4]-d[0],d[5]-d[1],
            d[7]-d[3],d[6]-d[2]};
        normal.setX(Lerp(    Lerp(gx[0],gx[1],iy.f),
            Lerp(gx[2],gx[3],iy.f),iz.f));
        normal.setY(Lerp(    Lerp(gy[0],gy[1],ix.f),
            Lerp(gy[2],gy[3],ix.f),iz.f));
        normal.setZ(Lerp(    Lerp(gz[0],gz[1],ix.f),
            Lerp(gz[2],gz[3],ix.f),iy.f));
        normal        =    normal.normalized();
#else
        normal        =    btVector3(d[1]-d[0],d[3]-d[0],d[4]-d[0]).normalized();
#endif
        /* Distance    */
        const btScalar    d0=Lerp(Lerp(d[0],d[1],ix.f),
            Lerp(d[3],d[2],ix.f),iy.f);
        const btScalar    d1=Lerp(Lerp(d[4],d[5],ix.f),
            Lerp(d[7],d[6],ix.f),iy.f);
        return(Lerp(d0,d1,iz.f)-margin);
    }
    //
    void                    BuildCell(Cell& c)
    {
        const btVector3    org=btVector3(    (btScalar)c.c[0],
            (btScalar)c.c[1],
            (btScalar)c.c[2])    *
            CELLSIZE*voxelsz;
        for(int k=0;k<=CELLSIZE;++k)
        {
            const btScalar    z=voxelsz*k+org.z();
            for(int j=0;j<=CELLSIZE;++j)
            {
                const btScalar    y=voxelsz*j+org.y();
                for(int i=0;i<=CELLSIZE;++i)
                {
                    const btScalar    x=voxelsz*i+org.x();
                    c.d[i][j][k]=DistanceToShape(    btVector3(x,y,z),
                        c.pclient);
                }
            }
        }
    }
    //
    static inline btScalar    DistanceToShape(const btVector3& x,
        btCollisionShape* shape)
    {
        btTransform    unit;
        unit.setIdentity();
        if(shape->isConvex())
        {
            btGjkEpaSolver2::sResults    res;
            btConvexShape*                csh=static_cast<btConvexShape*>(shape);
            return(btGjkEpaSolver2::SignedDistance(x,0,csh,unit,res));
        }
        return(0);
    }
    //
    static inline IntFrac    Decompose(btScalar x)
    {
        /* That one need a lot of improvements...    */
        /* Remove test, faster floor...                */
        IntFrac            r;
        x/=CELLSIZE;
        const int        o=x<0?(int)(-x+1):0;
        x+=o;r.b=(int)x;
        const btScalar    k=(x-r.b)*CELLSIZE;
        r.i=(int)k;r.f=k-r.i;r.b-=o;
        return(r);
    }
    //
    static inline btScalar    Lerp(btScalar a,btScalar b,btScalar t)
    {
        return(a+(b-a)*t);
    }



    //
    static inline unsigned int    Hash(int x,int y,int z,btCollisionShape* shape)
    {
        struct btS
        {
            int x,y,z;
            void* p;
        };

        btS myset;

        myset.x=x;myset.y=y;myset.z=z;myset.p=shape;
        const void* ptr = &myset;

        unsigned int result = HsiehHash<sizeof(btS)/4> (ptr);


        return result;
    }
};


#endif
